Secure Encryption Technique(SET) :A Private

Key Cryptosystem

Avishek Datta Sambit Ghosh Souradip Nath Siladitya Chakrabarti

Index:= Introduction What is Cryptography Cipher Keys What is SET Usage of Keys Algorithms: Key Generation and Storage Testing and Analysis Conclusion

Introduction:= 21st Century is a digital age where need for computers is paramount. From education and research to infrastructure and defence, the use of computers has eventually spread into everything. Every day billions of bits of data are being passed from one end of the world to other. With this volume of data being transferred from one place to other, the need for securing the data has become paramount. This is where the role of Cryptography and Information Security plays an important part. The Secure Encryption Technique (SET) brings about such an algorithm which depends completely upon the design and the form of the Key used by the user to encrypt the message. The more complex the key becomes, the more difficult the cipher text becomes to analyse. According to the test results prepared from the testing between the plain text files and the cipher text files, SET has given approximately 25% better results in terms of Chi-Square values and Encryption--Decryption Time.

What is Cryptography?Cryptography is a method of storing and transmitting data in a particular form so that only those for whom it is intended can read and process it.

“The aim of cryptography is to produce an algorithm to secure communication where any unwanted third party would not be able to read the transmission.”

Cipher:= In cryptography, a cipher (or cypher) is an algorithm

for performing encryption or decryption—a series of well-defined steps that can be followed as a procedure.

Cipher text is also known as encrypted or encoded information because it contains a form of the original plaintext that is unreadable by a human or computer without the proper cipher to decrypt it. Decryption, the inverse of encryption, is the process of turning cipher text into readable plaintext.

Symmetric Cipher:

When same key is used to encrypt and decrypt the message it is called Symmetric Cipher.

The keys may be identical or there may be a simple transformation to go between the two keys.

Asymmetric Cipher:

Asymmetric Encryption is a form of Encryption where keys come in pairs. What one key encrypts, only the other can decrypt.

In Asymmetric Cryptography two different types of keys are used for encryption and decryption. One is public key and another one is private key.

Keys:

There are two types of keys: Public Key Private Key

Public Key and Private Key:

The Public Key is what its name suggests - Public. It is made available to everyone via a publicly accessible repository or directory.

On the other hand, the Private Key must remain confidential to its respective owner.

Because the key pair is mathematically related, whatever is encrypted with a Public Key may only be decrypted by its corresponding Private Key and vice versa.

What is SET:= The Secure Encryption Technique (SET) is a Private Key

Block Cipher Cryptosystem which has been modified on the platform of Triple SV.

This cryptosystem inherits its basic architecture and function from TSV and then it has been developed further to provide better security with the ease of use for even the basic requirements of encryption system.

The key is a 27 bit (128 bit) key and the encryption is

based completely on the key provided . Key words: TSV, Private Key Cryptosystem, Block Cipher.

What is TSV(Triple SV):=

The Triple SV is a block cipher that uses secret key encryption.

This algorithm (SET) takes a fixed-length string of plaintext bits and transforms it through a series of complicated operations into another cipher-text bit string of the same length.

The proposed block size is 256 bits. The key comprises 128 bits .

Final Stage:=

At the end of the encryption operation, the result will be a cipher-text of the same number of bits as the plain-text in a file of designated type.

The encryption is based on 2^7 (128) times, i.e. the encryption has 7 levels with each level containing the operations of encryption or decryption.

Usage of Keys:= The key, i.e. Private Key is generated with the help

of a passcode accepted from the user as input. In this case the passcode has been restricted to 7 characters only.

The key is stored in a file of designated type in respective archives.

It can be shared after being encrypted with light encryption algorithms like RSA, SHA, etc.

Algorithms:=

Algorithm of SET during Encryption

The encryption levels include three levels:

Near swapping, Far swapping

and Bitwise XOR

operation.

Algorithm of SET during Decryption

Near Swapping:=

n-bit Near Swapping Operation

The Near Swapping is another protocol where the string of data is swapped on a running pair basis. The first set of pair would include a swap between the first two

(i.e. 1st and 2nd)bits. The next swap would be between the next pair of bits (i.e. 3rd and 4th) bits and so on till the nth bit is swapped with (n-1)th bit. The resultant array would have a jumbled up set of Messages.

Far Swapping:=

n-bit Far Swapping Operation

The Far Swapping is a simple substitution protocol whereby the furthest of the bits in an array are swapped.

This means in an array of n bits, the 1st and the nth bit will be swapped in the first iteration and so on till n/2 bits. At the end of the entire operation, the initial string would be reversed.

This operation will be performed till the counter reaches n/2th

bit.

Bitwise XOR operation:= The bitwise XOR operation is performed after the near swapping stage . This protocol requires the use of a bit of the key. For each level, a bit of the key is selected and the XOR operation is performed with each character of the data string. The result of the operation will be stored in the same array. The operation is repeated the number of times as the quantity of the level.

n-bit Encryption Stages

KEY GENERATION AND STORAGE:=

The key is the second most important part of this encryption technique.

It is taken from the user as an input. After encryption, this key is stored in binary form in a .dll file.

This key can be shared after using light encryption like RSA, SHA,

KEY DISTRIBUTION TECHNIQUES:=

Symmetric Key Distribution Using Symmetric Encryption.

Symmetric Key Distribution Using Asymmetric Encryption.

Testing and Analysis:= Non Homogeneity Test:=

A way to analyse the technique is to test the non-homogeneity of the source and encrypted file .

The Chi-Square test has been performed for this purpose. The results are compared to some of the most popular encryption techniques.

Comparison of Chi-Square Values of ROBAST, RSA,TMAT, TMAT, TPRT, SRAT, TSV, SET

Encryption Time:=

The encryption time is the time required to convert a plaintext into a cipher text .

The SET being on the same platform as that of the TSV (Triple SV), has similar characteristics; however, on further evaluation, it was found that the SET has lower encryption time than that of TSV.

Encryption Time of ROBAST, RSA, TMAT, TPRT, SRAT, TSV, SET

The decryption time is the time required to convert a cipher text into a plaintext .

The SET being on the same platform as that of the TSV (Triple SV), has similar characteristics; however, on further evaluation, it was found that the SET has slightly higher decryption time than that of TSV.

The main difference in the decryption sequence between TSV and the SET remains is the presence of unique and user key based initialization vector.

Decryption Time:=

Decryption Time of ROBAST, RSA, TMAT,, TPRT, SRAT, TSV, SET

Avalanche Ratio Test:= The Avalanche Ratio test is perhaps the most

comprehensive test when it comes to analysis of a Cryptographic Algorithm.

The Avalanche Test is the ratio of difference between the simple encrypted file and one bit modified source key/file.

The Avalanche Ratio is the key of measure of cryptanalysis. In general terms, it is the measure that in what extent the characters/bits in the encrypted file will differ if we modify some characters/bits in the source file or in the session key.

1 2 3 4 5 6 7 8 9 10

020406080

100

Avalanche Ratio

ROBASTRSATPRTTMATSRATTSVSET

File Number

Ava

lanc

e Ra

tio V

alue

s

Chart comparing the Avalanche Ratio values of ROBAST, RSA, TPRT, TMAT, SRAT, TSV and SET

Conclusion:=

Thus, the SET is a symmetric block cipher using a 256-bit block and 128-bit key. From the above stated facts, it can be inferred that SET is a

promising new cryptosystem which can be used in various fields such as tele-communications, data security, cloud computing, etc.

The 128-bit standard encryption key length along with its Avalanche Ratio makes it safe against brute force attacks. Even the time complexity of this algorithm is proved to be better than the existing major cryptosystems such as RSA and TMAT.

Thank You Avishek Datta (10900110026) Sambit Ghosh (10900111079) Souradip Nath (10900111102) Siladitya Chakrabarti(10900111096)